1. Field of the Invention
The present invention relates to a double planetary carrier for carrying therein two sets of planet gears which are axially set apart from each other.
2. Description of Related Art
As this kind of double planetary carrier, there is conventionally known one in Japanese Published Unexamined Utility Model Registration Application No. 121451/1987. In this carrier, three pieces of side plates are disposed with an axial distance from each other. These side plates are integrally connected together via intermediate pieces which are interposed among the side plates. Planet gears are carried in a respective space between the intermediate side plate and the two side plates which are positioned on axially both outer sides thereof.
In an ordinary planetary carrier for carrying therein one set of planet gears, its assembling is carried out as follows. Namely, planet gears are inserted into the space between a pair of side plates which are connected together via intermediate pieces. Gear shafts for rotatably supporting the gears are then assembled to extend across both side plates. Both ends of the gear shafts are thereafter caulked to fix the gear shafts to the carrier.
However, in the above-described conventional double planetary carrier in which three pieces of side plates are integrally connected together, it is impossible to caulk those fitting ends of the gear shafts against the intermediate side plate. Therefore, the fitting ends of the gear shafts against the outer side plates have to be welded to the outer side plates to fix the gear shafts to the carrier. It follows that the welding of the gear shafts is time-consuming and the productivity becomes poor.
In order to eliminate this kind of disadvantage, the following arrangement may be considered. Namely, two pieces of carriers, each having a pair of side plates which are connected together via intermediate pieces, are provided so as to carry planet gears in each of them, and these two carriers are connected together to constitute a double planetary carrier. In this case, however, the problem will be how the relative positional accuracy between the two sets of planet gears can be secured. In other words, in the double planetary carrier of the above-described conventional example, since the gear shafts of the two sets of planet gears are respectively fitted onto the intermediate side plate, the relative positional accuracy of the two sets of planet gears can be secured with the intermediate side plate serving as a reference or a basis. However, in case the two sets of planet gears are to be carried by separate carriers, it becomes difficult to maintain the relative positional accuracy of the two sets of planet gears due to manufacturing tolerance of each carrier, positioning tolerance in connecting the carriers together, or the like.
In view of the above-described disadvantages, the present invention has a first object of providing a double planetary carrier in which two sets of planet gears are carried in separate carriers and in which the relative positional accuracy between the two sets of planet gears can also be secured.
Further, the lubrication between the gear shafts for rotatably supporting the planet gears and the planet gears is conventionally carried out in the following manner. Namely, each gear shaft is supported in a throughgoing manner by penetrating it through side plates of the carrier. A bottomed oil hole is drilled on an end surface of each gear shaft so as to extend along the axial line of the gear shaft. A small oil hole is provided to communicate a substantially central portion of a cylindrical surface, which is a bearing portion of the gear shafts, with the oil hole to thereby supply the bearing portion with lubricating oil from the oil hole via the small oil hole. However, the lubricating oil will not enter the oil hole by simply opening the oil hole in the end surface of each gear shaft. As a solution, as described in Japanese Published Unexamined Utility Model Registration Application No. 117464/1979, the following arrangement is known. Namely, a ring-like thin plate which covers, with a clearance, an end surface of each gear shaft is mounted such that its peripheral edge is closely attached to a side plate of a carrier. A pocket-like space, to which an opening portion of an oil hole faces, is formed so that the lubricating oil entering the pocket-like space through centrifugal force can be introduced into the oil hole.
Suppose that the above-described conventional lubricating means is applied to the double planetary carrier which carries therein two sets of axially set apart planet gears as described in the above-described Published Unexamined Utility Model Registration Application No. 121451/1987. Each oil hole is made to open, out of both end surfaces, into that end surface of each gear shaft supporting each planet gear which lies on the outer side surface, and a ring-like thin plate is also provided on respective outer surface. However, since the ring-like thin plate must be mounted with a clearance from the end surface of each gear shaft as described above, there is a disadvantage in that each of the ring-like thin plates protrudes out of the side plate and consequently that the axial dimension of the carrier becomes large.
In view of the above-described disadvantage, the present invention has a second object of providing a double planetary carrier in which the gear shafts and the planet gears can sufficiently be lubricated without using the above-described ring-like thin plates.
According to the present invention, the above-described first object is attained by a double planetary carrier for carrying therein two sets of planet gears, one set being axially set apart from the other set, comprising: a first carrier having a pair of side plates which face each other with one set of said planet gears on one axial side being interposed therebetween, said side plates being connected together via intermediate pieces; a second carrier having a pair of side plates which face each other with the other set of said planet gears on the other axial side being interposed therebetween, said side plates being connected together via intermediate pieces, the side plate on the other axial side of said first carrier being defined to be a first side plate, the side plate on the one axial side of said second carrier being defined to be a second side plate; wherein said first side plate and said second side plate are disposed axially opposite to each other; one of said first side plate and said second side plate has on a periphery thereof a cylindrical portion for receiving therein the other of said first side plate and said second side plate; and said cylindrical portion and a periphery of the other of said first side plate and said second side plate have serrated teeth for engagement with a play therebetween, whereby said first carrier and said second carrier are engaged by means of serrations.
In order to function as a double planetary carrier, the torque transmission between the first carrier and the second carrier must be made without failure. This requirement can be met by engaging the two carriers by means of serrations.
Further, since the serrated engaging portion is provided with a play, both carriers are relatively diametrically movable when the two sets of planet gears are engaged with the sun gears. Therefore, the two sets of planet gears are automatically aligned relative to the sun gears with the result that the relative positional accuracy of the two sets of planet gears can be secured.
According to another aspect of the present invention, the above-described second object can be attained by a double planetary carrier for carrying therein two sets of planet gears, one set being axially set apart from the other set, comprising: a first carrier having a pair of side plates which face each other to support, in a throughgoing manner, gear shafts which rotatably support one set of said planet gears on one axial side, said side plates being connected together via intermediate pieces; and a second carrier having a pair of side plates which face each other to support, in a throughgoing manner, gear shafts which rotatably support the other set of said planet gears on the other axial side, said side plates being connected together via intermediate pieces, the side plate on the other axial side of said first carrier being defined to be a first side plate, the side plate on the one axial side of said second carrier being defined to be a second side plate; wherein said first side plate and said second side plate are connected together in a manner axially opposite to each other; each of said gear shafts has an oil hole which opens into an end surface thereof which is exposed to facing surfaces of said first side plate and said second side plate; and radial grooves are provided between said first side plate and said second side plate so as to reach opening portions of said respective oil holes.
According to this double planetary carrier, grooves to introduce by centrifugal force lubricating oil to the oil hole of each gear shaft are secured in that space between the first side plate and the second side plate which serves as a connecting portion between the first carrier and the second carrier. Therefore, it becomes not necessary any more to mount a conventional ring-like thin plate on the axially outer side of each carrier. It is thus possible to shorten the axial dimension of the double planetary carrier without impairing the ease with which the lubricating oil can be supplied.
It is acceptable to cut or provide grooves on the facing surfaces of the first side plate and the second side plate respectively. However, if an oil plate provided with radial grooves is interposed between the two side plates, the grooves can be easily and advantageously secured.